The purpose of this project is to develop an immunoassay that can be used in screening programs for determination of blood lead levels. Monoclonal antibodies specific for delta-aminolevulinic acid (ALAD) and lead will be used to investigate the feasibility of their use for detection of lead bound to ALAD in an erythrocyte lysate. The system will be evaluated first with purified ALAD containing known amounts of lead. An ALAD-specific antibody will be adsorbed to a solid phase and used to capture the lead-containing ALAD. The lead-specific antibody will then be used in an ELISA to quantify the amount of lead bound to the ALAD and compare the results to those obtained by atomic absorption. After successful completion of these experiments, human blood samples containing known amounts of lead will be substituted for the ALAD in the assay. Erythrocytes will be lysed with a nonionic detergent, and the ALAD- specific antibody will be used to capture the released ALAD. The lead- specific antibody will then be added for detection by ELISA of lead bound to ALAD. The results will be correlated with the lead concentrations in the blood samples determined by anodic stripping voltametry or graphite- furnace atomic absorption.